Shops displaying valuable items should be fitted with monitoring and/or alarm devices to prevent such items from being stolen. An example of monitoring device comprises monitoring cameras installed on the premises where valuable items are displayed. According to an example, the alarm device comprises a sensor capable of detecting the removal of an object from its display and an emitter of a sound alarm when the object is removed from the display. According to another example, the alarm device transmits an alert signal when an item is removed from its display, for example, to the police or to a security service.
However, such devices are not efficient in the case of armed robberies. Indeed, in this type of theft, robbers do not mean to act inconspicuously. The robbers may further be masked to avoid being recognized on video images. Further, because of the short duration of the robbery, the robbers may have already left the premises before the police or a security service can intervene.